The present invention relates to adaptive control systems.
Adaptive control systems are closed loop systems in which the gain of the system is varied according to the system's response to events that disturb it. While most controlled processes have response characteristics which vary only slightly over their entire range of operation, there are other systems where the operating characterics vary substantially. For example, a crane or the arm of a robot has different response characteristics depending on the weight of an object being moved. Many other controlled systems or processes have changing response characteristics in different portions of their operating range. One consequence is that a forward gain which provides a stable response in one portion of the operating range may make the system unstable in another portion of the operating range. For these types of controlled systems an adaptive control rather than a fixed gain control is desirable.
Most adaptive control systems have depended on knowledge of the controlled system's response characteristic. Some adaptive controllers have applied white noise to the controlled system input to determine the controlled system's response characteristics. Other adaptive controllers have superimposed discrete interval binary noise on a controlled system's input in order to determine the controlled system's response characteristics. Still other adaptive controls have used a mathematical model of the controlled system. The model is fed control signals at the same time that the real system is fed the same control signals. The actual system's response and the model system's response are compared and any difference is used to adjust the actual system's forward gain until the actual system behaves just like the model.